With the advantages of long life, energy saving, environmental friendly and shake-resistant, the LED light sources can be applied in a wide area. With the development of manufacture technology, the cost of the LEDs becomes lower and lower, and the optical efficiency is increased a lot. It is a trend that solid-state lighting (SSL) replaces the traditional lighting devices.
The US Energy Star criteria have certain requirements for omnidirectional SSL replacement lamps (shown in FIG. 1). Within 0° to 135° zone, luminous intensity at any angle shall not differ from the mean intensity for the entire 0° to 135° zone by more than 20%. Flux within 135° to 180° zone shall occupy at least 5% of the total flux. Measurement results should be the same in vertical plane 45° and 90° from the initial plane. Most of the LEDs' intensity distribution is lambertian rather than uniform, so secondary optical design is indispensable. For SSL replacement lamps, in order to meet those requirements, it is essential to design optical components to redistribute light.
In the related art, there are many solutions to get light source redistribution for LED lamps. The first solution is optimizing LEDs' array, and the second solution is using reflector to redistribute light.
Patent with the number of WO2009/059125A1 discloses an optical assembly including a single LED lamp and a rotationally symmetrical reflective light transformer providing an omnidirectional pattern with a pre-calculated intensity distribution.
Patent with the number of EP2180234A1 discloses an omnidirectional light bulb containing a transparent body member and a contact member at an end of the body member that could be screwed into a conventional light bulb socket for establishing electrical connections. The light bulb also contains at least a disc and a supporting pole. A number of LEDs are back-to-back configured along the circumference of each disc, so as to realize the omnidirectional illumination.
Patent with the number of US2002/0114170A1 discloses an incandescent light source replaced with omnidirectional distribution. A light guide receives and guides light output from the light source. The light guide further extends out from the light source. A reflector is positioned in the light guide and reflects the light guided through the light guide to provide appropriate edge illumination.
Among all of the above solutions, no solution is proposed for achieving omnidirectional illumination through the design of a lens.